Automatic clamping device



Feb. 5, 1952 L. K. CLARK AUTOMATIC GLAMPING DEVICE 5 Sheets-Sheet l Filed March 7, 1950 Al -wv lllllllll INVENTOR LLOYD K. CLARK gym ATTORNEY Feb. 5, 1952 L. K. CLARK AUTOMATIC CLAMPING DEVICE 5 Sheets-Shee(I 2 Filed March 7, 1950 Hill l- INVENTOR LLOYD K. CLARK ATTORNEY Feb. 5, 1952 L.. K. CLARK 2,584,789

AUTOMATIC CLAMPING DEVICE I 10 ,9 Q K I- Q i ,o2 i I l l\ F Sb I Y# l I s LD z p 2 In PG N INVENTOR Eh T LLOYD K. CLARK BY O (0 Feb. 5, 1.952 L. K. CLARK AUTOMATIC CLAMPING DEVICE 5 Sheets-Sheec 4 Filed March 7, 1950 lNvr-:NTOR LLOYD K. CLARK BY A W ATTORNEY Feb. 5, 1952 L. K. CLARK INVENTQR LLOYD K. CLARK Patented F eb. 5, 1952 AUTOMATIC CLAMPIN G DEVICE Lloyd K. Clark, Owego, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application March 7, 1950, Serial No. 148,094

5 Claims. l y The presentI invention relates to milling machines of the kind wherein a matrix-is employed for the purpose of generating type faces on the periphery of a circular blank or workpiece by reciprocating the matrix and rotating the workpiece in alternate directions whereby continuous pressing and rolling action is aiiected between the matrix andthe workpiece. The invention is more lparticularly directed to a draw bar mechanism whichA cooperates with a suitable workholder to secure the workpiece during the type forming operation.

Machines of this general type have been in use for some time and it has been common practice 'to employ a draw bar rod which is mounted in the spindle of the machine and which supports an arbor. The arbor is secured in a socket of the spindle andboth are rotatable with the rod. The workpiece is placed between one end of the rod and the face of the arbor and is secured by screwing a nut on the end of the rod to press the workpiece against the arbor. This practice necessitates stopping the machine when the work is changed, for a time long enough to unscrew and remove such nut, remove the finished type wheel, apply a new wheel blank, and replace and tighten up the nut.

In a type forming operation of the kind where the type characters are rolled into the periphery of a wheel blank it is quite important that the wheel blank be held very securelyin order to obtain clear and accurate type characters. As a result it became necessary when inserting a new wheel blank on the rod to screw the nut by hand and then further tighten the nut by means of a wrench. Also when removing the type wheel atv the end of a type rolling operation it became necessary to'apply a wrench to the nut and then strike the wrench with a rather heavy hammer in order to loosen said nut. This Was due to the fact that during the type rolling operation the metal in the Wheel blank expands and increases the locking action between the nut and the related screw threads on the rod. The rolling operation itself takes approximately half a minute and since the replacement of the workpiece is therefore repeated at short intervals the added necessity of tightening and untightening the nut by means of a wrench and a hammer greatly increases the time required for rolling type wheels and adds considerably to the fatigue of the operator.

Accordingly it is the primary object of the invention to provide an improved automatic draw bar operating mechanism which will reduce the :Y:

time and eliort required in making exchange of Wheel blanks during the operation of rolling type faces on type wheels.

It is a feature of the invention to provide a means whereby the operator will be required only to place the workpiece in the workholder and to screw the nut with a minimum of linger pressure to a position whereby said workpiece will be but loosely held and to have the additional required tightening of the workpiece automatically effected by the machine at the start of each new type rolling operation. Thus, it is a further object of the invention to provide an improved draw bar mechanism wherein a draw bar is automatically moved horizontally along its axis and in one direction at the start of each new machine operation causing a take up in slack between associated workholding members mounted on said draw bar which results in tightening the workpiece into position.

It is a further feature of the invention to provide means automatically called into operation at the end of each type rolling operation to relax the grip on the workpiece to its original state of llooseness thereby enabling the operatorto remove Y the workpiece by merely unscrewing the nut with a minimum of iinger pressure. As a result it is a further object of the invention to provide an improved draw bar mechanism wherein a draw bar isA automatically moved horizontally along its axis and in one direction at the end of each type rolling operation to cause the associated workholding members mounted on said draw bar to slacken their grip on the workpiece.

A still further object of the invention is to provide a novel control mechanism for effecting a shifting movement ofthe draw bar in one direction at the start of a new type rolling operation 'and for eiecting movement of the draw bar in the opposite direction atthe end of a type rolling operation.

Other4 objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings: Fig. l is a view showing the outline of a side yelevation of "a standard milling machine with the standard part shapes shown in dotted lines and the new draw bar mechanism and associated parts shown in full lines'.

Fig. 2 is a view showing the outline of a front elevation of a standard milling machine with the standard part shapes shown in dotted lines and the new draw bar mechanism and associated parts shown in full lines.

Fig. 3 is a sectional view taken on line 3-3 of Fig. 5 and showing the entire length of the draw bar with all the associated parts that are around it.

Fig. 4 is a partial end view of the draw bar control mechanism showing the lock bolt in the retracted position.

Fig. 5 is an end view of the draw bar control mechanism showing the lock bolt in the extended position.

Fig, 6 is a partial end view of thedraw bar control mechanism showing the lock `bolt about to be cammed fee from the lock cam.

Fig. 7 is a perspective view showing the spindle cam and the lock cam disassembled from each other.

The invention is illustrated in connection with a standard commercial milling machine and inasmuch as the provisions in such machine for reciprocating the horizontally moving .bed having a matrix mounted thereon, rotating the workpiece, and feeding the bed and matrix to depth in the workpiece are all standard, and are not affected by the new invention here disclosed, I have limited the detailed showing of the drawings to those features only which are necessary to an explanation of the new steps .and features, and for the rest have shown simply the external outlines of the machine.

By way of general explanation, it will be sufficient to say that IU (Fig. 1) represents the rotatable machine spindle to which is attached a holding arbor II; that I2 represents a support plate which is bolted to the top surface of the horizontally moving bed of the machine and that the bed is caused to reciprocate by a hydraulic pump arrangement which is a standard part of the machine; that a floating rack I3 is mounted on the support plate I2 and meshes with a gear I4 xed to said arbor II thereby causing the arbor II and spindle I0 to rotate as the horizontally moving bed is reciprocated; and that said support plate I2 also supports a die rack vor matrix 2.

I5 which is moved in either direction vertically for swaging pressure by means of a, hydraulic pump arrangement acting upon said horizontally moving bed in a manner common to standard milling machines. further describe the various mechanisms in the milling machine which eifect the aboveA mentioned movements since these mechanisms are a minor part of the showing of the present invention and merely constitute a preferred mode for carrying out the principles of the invention.

The construction of the draw bar mechanism can best be seen by referring to Figs. l and 3. The machine spindle Ic is rotatably mounted in the milling machine in the usual manner and extends all the way through the machine as shown in Fig. l. A tapered hole IB extends through a portion of said spindle I@ and is adapted to receive the tapered end of the arbor II as shown in Fig. 3. This arbor II is rigidly attached to the spindle I for rotation therewith by means of the screws Il' and both the arbor II and the spindle II! are adapted to receive a draw bar I8. The draw bar I8 is slidably mounted .within said arbor I I and spindle I0 so that it may It is not deemed necessary to Ur v screw I9 and groove 20 also serve as a means for making said draw bar I8 rotatable with said arbor II and spindle I.

As was previously mentioned, in generating type about the periphery of a workpiece, the workpiece is rotated in alternate directions while in .rolling contact with the matrix. Accordingly, there is provided a means for rotating the arbor I I in alternate directions which -comprises a gear I4 rigidly attached to said arbor i I and in mesh with a floating rack i3 as shown in Fig. 1. The floating rack I3 is spring mounted in a support plate I2 which is in turn bolted to the top of the horizontally moving bed 2| of the machine. Standard commercial hydraulic pumps are provided within the machine which communicate a suitable working luid through the tubings indicated at 22 and 23 in Fig. 1 to give the bed 2I horizontal reciprocating motion and vertical motion.

Referring to Fig. l, it can be seen that the draw bar mechanism protrudes out from the front of the machine to facilitate the mounting of the workpiece thereon. As shown in Fig. 3, the arbor II has a shaft-like portion 24 on which is suD- ported the workpiece 25 and a pair of holding face plates or collars 26 and 2l. The collar 21 is loose axially on the shaft portion 24 but is in a xed relation to the main part oi the arbor II for rotation therewith by means of the pins 28. The workpiece 25 and collar 25 are also loosely mounted on said shaft. portion 24 to facilitate loading and unloading of the same by the operator. A clamp collar 29 and a knob 30 are used by the operator to clamp the workpiece in position prior to running the machine. The clamp collar 29 vts loosely over a flange 3l, which is an integral part of the draw bar I8, and iscaused to abut against the collar 26 by the knob 30 screwed onto the threaded end portion of the draw bar. Knob 3Dmay be either a full nut, or of the quick fastening half nut type shown. Since the draw bar I8 automatically causes an additional force to be exerted against the collar 26 to effect a tighter grip on the workpiece, in a manner later described, it is only necessary that the operator turn the knob 30 a suicient amount to take up the initial slack between the collars and the workpiece.

The opposite end of the draw bar mechanism protrudes from the rear of the machine as shown in Fig. l and is supported in a bearing support 32 attached to the machine. Referring to Fig. 3, the rear end of the spindle I0 has a projection 33 which is adapted to receive a spindle cam 3Q. The spindle cam 34 is loose with respect to the draw bar I8 but is fixed to the spindle I0 for rotation therewith by means of a pin 35. A lock cam 3E is mounted losely on a shaft-like projection 31 of the spindle cam 34 and is held thereon by means of a collar 38, a washer 39, a collar nut ci) and a lock nut 4i which are mounted on the end of the draw bar I8 as shown in Fig. 3. Also the cam face 46 of lock cam 35 is maintained against the cam face 44 of spindle cam 34 for cooperation therewith by means of a coil spring 42 which presses between the flange SI of the draw bar and the front end portion 24 of arbor II. As such, the spring 42 tends to push the draw bar i8. towards the front of the machine and the collar 38 will force the lock cani 5 against the cam face 44 of the spindle arm 34.

The connguration of the cam faces of said cams 34 and 36, which are of the face cam variety, may 4best be seen by referring to Fig.

The face of spindle cam 34 -is ming surfaces 43 and 44 are identical in lead of f spiral and on each surface the lead of the spiral is in the same rotative direction, which looking at Fig. 7, would be clockwise. The face of lock cam 36 is also split down the middle and has two camming surfaces 45 and 46 opposite to but identical in lead of spiral to the surfaces 43 and 44.- When the two cam faces are juxtaposed as vshown in Fig. 3, the camming surfaces 45 and 46- are complementary to the camming surfaces 43and 44. It follows then that if, for example, cam 36 is held against rotation but is capable 'of movement along its axis and cam 34 is not capable of movement along its axis Vbut may be caused' to rotate in the same direction as the lead of spiral on the face of cam 36, then upon relative movement a wedging action will result wherein vthe surfaces 43 and 44 on cam 34 will force the Vlock cam 36 along the projection 31 and towards the rear of the mechanism.

Referring to Fig. 3, it may be seen that as lock cam 36 moves towards the rear of the mechanism it willforce the collar 38, washer 39, collar nut 46 and lock nut 4| to move in the same direction. y Since the lock nut 4| is fixed to the draw bai" I8, said draw bar will also move towards 'the rear of the mechanism, the camming force being greater than the opposing force of coil spring cam 34 be rotated in the opposite direction, i. e. .v-

in a rotative direction opposite to the lead of spiral of said lock cam 35, the wedging act-ionA pre-l viously described will be reversed and camy 36 will move back along the shaft-like projection '31 to its original position under the force ofthev coil spring 42 pressing against flange 3|. Hence.. the draw bar will be restored to its originalA position and the clamping grip exerted on the workpiece 25 by the various collars will be slackened.

I In' order tocontrol the operation of `spindlecan 34 and lock cam 36 to eiect the movements 'of the draw bar I6 just described, there isipro- Avided a control mechanism as shown in'Figs..

'-4,' 5 and 6. The main portion of the control mechanism, which is one of the features'of" the present' invention, is shown as being incorporated "in 'a support block 41 dovetailed onto the frame of the milling machine and held in place` bya bolt 48, Fig. 5. The support block 41 is in the extreme rear portion of the machine (Fig. 1) and houses the lock cam 36 (Figs. 3 and 4) with which said control mechanism coacts. Y

The means provided for operating the control `mechanism comprises lstandard commercial devices and need only'be pointed out and not den .scribed in detail. Air under pressure is communif .cated froma suitable source through .a tubing 45j (Fig.v l) and into a commercial solenoid operated air valve 56 mounted to the machine frameg. The airl is further communicated between the' air .valve 56 and an air cylinder 5| by means of the tubes 52 and 53, said air cylinder 5| being bolted to the side'of the support block 41. and having a conventional plunger 54 which is connected to the control mechanism. The operator may control the movement of said plunger 54 by means of a standard electrical control switch 55'which is mounted on the front of the machine as shown in Fig. 2. Tubing 56` conducts power wiring from said switch 55 through ajunction box 51 mounted on the side of the machine (Fig. l) to the solenoid of the air valve 50.

When power is on the machine, the air valve 50 allows air through tube 53 to maintain plunger 54 in the raised position in the cylinder 5|. When button 58 (Fig. 2) on switch 55 is depressed, vthe air valve 5D (Fig. l) will switch the air pressure to tube 52 to cause the plunger 54 to be'forced downward. Plunger 54 will be maintained in the lowered position as long as button 58 is held depressed and-can be returned to its raised position upon the release of said button.

The operating parts of the control mechanism are housed within a chamber 59 (Fig. 5) of the support block 41 and function particularly to control the rotation of the lock cam 36. This is done by actuating a lock bolt 66 and causing the same to seat into a notch 6| in the lock cam 36 to prevent the rotation thereof and then later retract the lock bolt 6D to free said cam '36 for rotation. A toggle mechanism is provided for actuating the bolt 60. The toggle comprises a pair of links'62 and 62a pivotally joined end to end by a stud 63. The stud 63 nts into an elongated Aslot 64 of an adapter 65 which is connected to the plunger 54. The other endof link 62 is pivotally mounted on 'a short shaft 66 fixed to the side plates of the support block 41 while the free end of link 62a is pivotally attached to'one end of the'bolt 66 by a stud 61. It follows then that with 'the bolt 60 in a retracted position as shown-in Fig. 4, a downward movement of the plunger 54 will tend to straighten the toggle mechanism and force the bolt 60 to seat in notch 6| as shown in Fig. 5. Conversely, an upward movement of the plunger 54 will retract the bolt 60' out of notch 6|. A block 68 attached to the bottom of chamber 59 provides a bearing surface for the joined ends o link 62a and b01t 60.

The free end of bolt 60 is supported in a horif zontal position by a spring plunger 69 mounted lin a spring housing unit10 attached to the under vside of the support block 41 -by the bolts 1|. A

the arbor and secured loosely against the collar 21 by manually turning the knobv36 a couple of timesrwith the collars 26 and 23 interposed. The lock cam 3 6 (Fig. 5) is then locked against rotation as previously described by depressing button 58 (Fig. 2) on switch 55. While holding said butjton 58 depressed, the operator starts'the machine by actuating the start switch indicated at 11 Yin Fig. 2, thereby setting into motion the hori'- zontallyv moving bed l2|. The'hydraulic pumps in the machine operate to start the vertical movement of the bed 2| to feed the matrix l5 against ,the periphery ofthe wheel blank and at the same time'cause said bed 2| to reciprocate horizontally,

rstrto the left and `thento the vright (looking at the front of the. machine as in Fig. 2). Wellknown means areA also provided on the machine which can be set by the operator to control the number of horizontal passes that bed 2| will make and also-the amount of vertical movement required depending upon the particularY type rolling operation involved.

As bed 2| (Fig. l) starts its initial pass toward the left, gear I4 will cause the arbor I I and spindle cam 34 to commence to rotate in a counterclockwise direction (Fig. 7) which is the same direction as the lead of spiral of the camming surfaces on lock cam 36. Only a few degrees of rotation of cam 34 are all that is necessary to force lock cam 36 a sufficient distance along projection 31 to cause a take-up of the looseness between the members along the draw bar I8 and rigidly clamp the type wheel blank 25 in position. The lead of spiral of the camming surfaces on cams 34 and e' 36 is such that as cam 34 continues to rotate further, a binding action occurs between said cams and the pressure exerted by the interacting cam surfaces will increase suiliciently to over:-

.come the pressure exerted against bolt 60 (Fig. 5)

that the action just described is completed in the matter of a few seconds and while the bed 2| iS still making its initial pass to the left.

As the bed 2| nears the end of its travel to the left a conventional limit switch indicated at I9 on Fig. 2 will be actuated in the usual manner to cause bed 2| to reverse its direction of move.- ment and move to the right. The spindle cam 34 (Fig. '7) will nowrotate in a clockwise direction and the binding action between said spindle cam 34 and the lock cam 36 is sufficient to cause said lock cam 36 to rotate clockwise with the spindle cam 34. When bed 2| nears the end of its movement to the right, the limit switch 19 will again be actuated causing the motion of said bed to reverse and accordingly reverse the rotation of cams 34 and 36. The bed 2| will reciprocate in this fashion to complete as many passes as the machine is set for. One pass is considered to have been made when the bed completes its travel in one direction.

Y Assuming that the operator has set the machine to make a total of six passes, at the` completion of the fth or next to the last pass, controls within the machine will cause the bed 2| to gradually feed downward. At this point the operatordepresses button 58 to lock cam 36 against any further rotation as previously described. The lock cam 36 will be rotating counterclockwise (looking at the front of the machine) and bolt 60 will strike the periphery of said cam and seat in the notch 6| (Fig. 5) as it comes around clockwise into position. The lock cam 36 will be stopped and heldin a stationary position because bolt 60 will be prevented by lock 'I5 from taking any upward travel. The spindle cam 34 (Fig. -'7) continues to rotate clockwise forapproximately 30 to 45, during which time bed 2| will have completed its movement to the right and the machine will stop. Since the spindle cam 34 was last rotatingV in a direction opposite to the lead of spiral en the surfaces ofcam 36, the draw bar I8 (Fig. 3) will move towards the front of the machine underl the force of coil spring 42, and the grip exerted -on the type wheel blank 25 by the various collars will be slackened. Meanwhile the bed 2| (Fig. 2) will have completed its downward movement, thus freeing the workpiece 25 from the matrix l5. The knob 3|) can be readily unscrewed merely by finger pressure. the finished type wheel removed and a new type Wheel blank inserted for the next operation.

Collar nut 40 and lock nut 4| may be adjusted on the draw bar I8 for different production runs that may involve type wheel blanks of different thicknesses and also to time the interaction of cams 34 and 36. Where a production run involves many type wheel blanks and it only requires around 6 or 8 passes of the machine to completely engrave each wheel it can be readily understood that use of the devices of present invention will result in a tremendous saving in time and effort.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a single modification, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention. therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a machine tool, a rotatable member, a draw 'bar adapted for axial movement within saidmember, a pair of juxtaposed face plates on said'member, one of said face plates being attached thereto and the other free for axial movement thereon, limit means secured on said draw bar to maintain said face plates juxtaposed, a second limit means secured on said draw bar and spaced apart from said rst means, a pair of complementary cams interposed between said limit means, one of said cams being attached to said member, said cams adapted upon rotationv to cam said second limit means to cause said draw bar and said rst limit means to apply a force against said face plates and member and upon a reversal of rotation to release said force. and control means adapted to lock one of said cams against rotation.

2. A machine tool of the kind set forth in claim 1 wherein said control means comprises a mechanism, a bolt attached to said mechanism and capable of axial movement, a fixed plate, a member adapted to support said bolt against said fixed plate, and means for operating said mechanism to cause said bolt to move between said fixed plate and member to lock one of said cams against rotation.

3. In' a machine tool, a rotatable member, a draw bar adapted for axial movement within said member, a pair of juxtaposed face plates on said member, one of said face pla-tes being attached thereto and the other free for axial movement thereon, limit means secured on said draw bar to maintain said face plates juxtaposed, a second limit. meansV secured on said draw bar and spaced apart from said first means, a pair of complementary cams interposed between said limit means, control means adapted to lock one of said cams against rotation, means to rotate said second cam when said first cam is locked to cam said second limit means to cause said draw bar and said rst limit means to apply a force against said face plates and member, yieldable means included in said control means and operable by a predetermined pressure resulting from the interaction of said cams to allow said iirst cam to free itself for rotation with said second cam and thereby maintain said force applied against said face plates, and means to operate said control means when said cams are rotating together in a reverse direction to lock said rst cam to release the force applied against said face plates.

4. In a machine tool for operating on a Workpiece, an arbor carrying said workpiece, a draw bar adapted for axial movement within said arbor, a pair of juxtaposed face plates on said arbor and on opposite sides of said workpiece, one of said face plates being attached thereto and the other free for axial movementl thereon, limit means adjustably secured on said draw bar to maintain said face plates and workpiece juxtaposed, a second limit means adjustably secured on said draw bar and spaced apart from said iirst means, a pair of complementary face cams interposed between said limit means, one of said cams being attached to said arbor, said` cams adapted upon rotation to cam said second limitl means to cause said draw bar and said rst limit means to apply a force against said face plates, workpiece and control means adapted to lock one of said cams against rotation to cause relative movement between the cams and a resultant camming action.

5. A machine tool as set forth in claim 4 wherein said control means comprises a toggle mechanism, a bolt attached to said mechanism and capable of axial movement, a fixed plate, a flexible member adapted to support said bolt against said xed plate, and means for operating-said mechanism to cause said bolt to move between said xed plate and said member to lock one of said cams positively against rotation in one direction and to permit movement of said one cam in the other direction only after it has exerted a camming and clamping force to the draw bar through wedging engagement of the two face cams.

LLOYD K. CLARK.

REFERENCE Sv CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 95,344 Hill Sept. 28, 1869 262,369 Cameron Aug. 8, 1882 998,274 Bredell July 18, 1911 1,065,951 Magrane July 1, 1913 1,723,785 Johnson Aug. 6, 1925 1,789,892 Allatt Jan. 20, 1931 1,796,387 Mountford Mar. 17, 1931 2,038,759 Roberts Apr. 28, 1936 

